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习题练习:2011 美国F=ma物理竞赛 F=ma physics competition



 作者: admin   总分: 25分  得分: _____________

答题人: 匿名未登录  开始时间: 23年12月09日 21:14  切换到: 整卷模式

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1#
 
单选题 ( 1.0 分) (组内1/1) 切至整卷模式 搜藏此题  
第 1 题组 (共 1 题 1 分)
  A cyclist travels at ag05ixw jdjq7d9zi4e38nacpwz6 ) e-c constant speed of $22.0 \mathrm{~km} / \mathrm{hr}$ except for a 20 minute stop. The cyclists average speed was $17.5 \mathrm{~km} / \mathrm{hr}$. How far did the cyclist travel?

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2#
 
单选题 ( 1.0 分) (组内1/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第1/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the average acceleraty hi.1gojij0q v( :9fiion during the ten second interval.

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3#
 
单选题 ( 1.0 分) (组内2/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第2/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the maximum velocio m xc:j.7p 8fil7+owfv5( sxdty achieved during the ten second interva8l5im( cp7wf:fox d+ .x vo7sjl.

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4#
 
单选题 ( 1.0 分) (组内3/3) 切至整卷模式 搜藏此题  
第 2 题组 (共 3 题 3 分) 当前第3/3题
题组内容描述:
Questions 1 to 3 refer to the three graphs below which show velocity of three objects as a function of time. Each object is moving only in one dimension.
  Rank the magnitudes of the distance traveled during the ten second intervalf3ig*o/9:mdbx d lmb9.

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5#
 
单选题 ( 1.0 分) (组内1/11) 切至整卷模式 搜藏此题  
第 3 题组 (共 11 题 11 分)
  A crude approximation is that the Earth travels in a circular orbit about t ql+i iw;e vanmrp)v:qtj(3qm.u)(7jhe Sun at c ;vmmwqre qiia7ptvn q(j3).j):u (+lonstant speed, at a distance of $150,000,000 \mathrm{~km}$ from the Sun. Which of the following is the closest for the acceleration of the Earth in this orbit?

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6#
 
单选题 ( 1.0 分) (组内2/11) 切至整卷模式 搜藏此题  
  A child is sliding out of control with velocrp3tkgvkg 3g u9/0yc9ity $v_{\mathrm{c}}$ across a frozen lake. He runs head-on into another child, initially at rest, with 3 times the mass of the first child, who holds on so that the two now slide together. What is the velocity of the couple after the collision?

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7#
 
单选题 ( 1.0 分) (组内3/11) 切至整卷模式 搜藏此题  
  An ice skater can rotate about a vertical axis with6+7r3 lftljq5xfwm8 e an angular velocity $\omega_{0}$ by holding her arms straight out. She can then pull in her arms close to her body so that her angular velocity changes to $2 \omega_{0}$, without the application of any external torque. What is the ratio of her final rotational kinetic energy to her initial rotational kinetic energy?

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8#
 
单选题 ( 1.0 分) (组内4/11) 切至整卷模式 搜藏此题  
  When a block of wood wiy x51 /m c9caqrvzifv rv17t40th a weight of $30 \mathrm{~N}$ is completely submerged under water the buoyant force on the block of wood from the water is $50 \mathrm{~N}$. When the block is released it floats at the
surface. What fraction of the block will then be visible above the surface of the water when the block is floating?

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9#
 
单选题 ( 1.0 分) (组内5/11) 切至整卷模式 搜藏此题  
  A spring has an equilibrium length of 2.0 meters and a spring constant of 10 ne xel9 yebg i04*w+evu;wtons/meter. Alice is pulling on one end of the sprinw0l * ieugexy 4be+v;9g with a force of 3.0 newtons. Bob is pulling on the opposite end of the spring with a force of 3.0 newtons, in the opposite direction. What is the resulting length of the spring?

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10#
 
单选题 ( 1.0 分) (组内6/11) 切至整卷模式 搜藏此题  
  Which of the following changes will result in an increasevg7iv/sq h(,td6 u :fb in the period of a simple pendulum?hg7b,u6(isdv/ :qft v

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11#
 
单选题 ( 1.0 分) (组内7/11) 切至整卷模式 搜藏此题  
  A large metal cylindrica f5gcws0i,k,nl cup floats in a rectangular tub half-filled with water. The tap is placed over the cup and turned w,g0i5nsfck, on, releasing water at a constant rate. Eventually the cup sinks to the bottom and is completely submerged. Which of the following five graphs could represent the water level in the sink as a function of time?


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12#
 
单选题 ( 1.0 分) (组内8/11) 切至整卷模式 搜藏此题  
  You are given a large collection 2;+4ulnu xp 4 qgug+qwi/dlq 3of identical heavy balls and lightweight rods. When two balls are placed at n/q4g p u3gqudiq+u+;2xl l4wthe ends of one rod and interact through their mutual gravitational attraction (as is shown on the left), the compressive force in the rod is $F$. Next, three balls and three rods are placed at the vertexes and edges of an equilateral triangle (as is shown on the right). What is the compressive force in each rod in the latter case?




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13#
 
单选题 ( 1.0 分) (组内9/11) 切至整卷模式 搜藏此题  
  The apparatus in the diagram consists of a solid cylinder of radiu +(a mv-lm5 eu8rt5ck00 paaqcs $1 \mathrm{~cm}$ attached at the center to two disks of radius $2 \mathrm{~cm}$. It is placed on a surface where it can roll, but will not slip. A thread is wound around the central cylinder. When the thread is pulled at the angle $\theta=90^{\circ}$ to the horizontal (directly up), the apparatus rolls to the right. Which below is the largest value of $\theta$ for which it will not roll to the right when pulling on the thread?




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14#
 
单选题 ( 1.0 分) (组内10/11) 切至整卷模式 搜藏此题  
  You have 5 different strings w ,)keh xs(r,b.wtc;k kith weights tied at various point, all hanging from the ceiling, and reaching down to the floor. The string is released at the top, allowing the weights to fall. Which one;kswe,tr kbk.hx) ,c( will create a regular, uniform beating sound as the weights hit the floor?


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15#
 
单选题 ( 1.0 分) (组内11/11) 切至整卷模式 搜藏此题  
  A vertical mass-spring oscillator is displaced5 rhs5spobc,*;/ caf7t ovo plb 3m:f5 $2.0 \mathrm{~cm}$ from equilibrium. The $100 \mathrm{~g}$ mass passes through the equilibrium point with a speed of $0.75 \mathrm{~m} / \mathrm{s}$. What is the spring constant of the spring?

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16#
 
单选题 ( 1.0 分) (组内1/2) 切至整卷模式 搜藏此题  
第 4 题组 (共 2 题 2 分)
题组内容描述:
Questions 1 and 2 refer to the information and diagram below.Jonathan is using a rope to lift a box with Becky in it; the box is hanging off the side of a bridge, Jonathan is on top. A rope is hooked up from the box and passes a fixed railing; Jonathan holds the box up by pressing the rope against the railing with a massless, frictionless physics textbook. The static friction coefficient between the rope and railing is $\mu_{s}$; the kinetic friction coefficient between the rope and railing is $\mu_{k}<\mu_{s}$; the mass of the box and Becky combined is $M$; and the initial height of the bottom of the box above the ground is $h$. Assume a massless rope.
  What magnitude force does Jonathan need to exert on th ( t,iwvh9ph+umy:0d0/ln7qkn o2a v pe physics book to keep the rp0n(qum9 v :wpn2v, o/k7ah l yt+id0hope from slipping?

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17#
 
单选题 ( 1.0 分) (组内2/2) 切至整卷模式 搜藏此题  
  Jonathan applies a normal force that is just enough to keep the rope from slip*ktev6ez+gbrj -/yed l 5:z )aping. Becky makes a small jump, barely leaving contact with the floor of the box. Upon landing on the boxze*)/g+e6rly v b :j5- detazk, the force of the impact causes the rope to start slipping from Jonathans hand. At what speed does the box smash into the ground? Assume Jonathans normal force does not change.

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18#
 
单选题 ( 1.0 分) (组内1/1) 切至整卷模式 搜藏此题  
第 5 题组 (共 1 题 1 分)
  A block of mass $m=3.0 \mathrm{~kg}$ slides down one ramp, and then up a second ramp. The coefficient of kinetic friction between the block and each ramp is $\mu_{\mathrm{k}}=0.40$. The block begins at a height $\mathrm{h}_{1}=1.0 \mathrm{~m}$ above the horizontal. Both ramps are at a $30^{\circ}$ incline above the horizontal. To what height above the horizontal does the block rise on the second ramp?

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19#
 
单选题 ( 1.0 分) (组内1/2) 切至整卷模式 搜藏此题  
第 6 题组 (共 2 题 2 分)
题组内容描述:
Questions 1 and 2 refer to the following information
A particle of mass $2.00 \mathrm{~kg}$ moves under a force given by
$$\vec{F}=-(8.00 \mathrm{~N} / \mathrm{m})(x \hat{i}+y \hat{j})$$
where $\hat{i}$ and $\hat{j}$ are unit vectors in the $x$ and $y$ directions. The partricle is placed at the origin with an initial velocity of $\vec{v}=(3.00 \mathrm{~m} / \mathrm{s}) \hat{i}+(4.00 \mathrm{~m} / \mathrm{s}) \hat{j}$.
  After how much time will the particle first85p. f*d) ilzfdko ruek 17u4m return to the origin?

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20#
 
单选题 ( 1.0 分) (组内2/2) 切至整卷模式 搜藏此题  
  What is the maximum distance betwee 36shrecozkaob4itk6a4: 7i; n the particle and the origin?

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21#
 
单选题 ( 1.0 分) (组内1/5) 切至整卷模式 搜藏此题  
第 7 题组 (共 5 题 5 分)
  An engineer is given a +i1ce* xot bj6d,0hnafixed volume $V_{m}$ of metal with which to construct a spherical pressure vessel. Interestingly, assuming the vessel has thin walls and is always pressurized to near its bursting point, the amount of gas the vessel can contain, $n$ (measured in moles), does not depend on the radius $r$ of the vessel; instead it depends only on $V_{m}$ (measured in $\mathrm{m}^{3}$ ), the temperature $T$ (measured in $\mathrm{K}$ ), the ideal gas constant $R$ (measured in $\mathrm{J} /(\mathrm{K} \cdot \mathrm{mol})$ ), and the
tensile strength of the metal $\sigma$ (measured in $\mathrm{N} / \mathrm{m}^{2}$ ). Which of the following gives $n$ in terms of these parameters?

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22#
 
单选题 ( 1.0 分) (组内2/5) 切至整卷模式 搜藏此题  
  This graph depicts the torque output of a hypothetical gasoline engine as a fv(ga/x 4w x8pjunctiongw pa/4jx xv8( of rotation frequency. The engine is incapable of running outside of the graphed range.


At what engine RPM (revolutions per minute) does the engine produce maximum power?

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23#
 
单选题 ( 1.0 分) (组内3/5) 切至整卷模式 搜藏此题  
  A particle is launched fh9lgf8 9ddx1-d7b+ im2aegef rom the surface of a uniform, stationary spherical planet at an angle to the vertical. The particle travels in the absence of air resistance and eventually falls back onto the planet. Spaceman Fred describes the path of the particle as a parabola using the laws of projectile motion. Spacewoman Kate recalls from Keplers laws that every bd1e7mx gb ffhli+dga 9 e9-82dound orbit
around a point mass is an ellipse (or circle), and that the gravitation due to a uniform sphere is identical to that of a point mass. Which of the following best explains the discrepancy?

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24#
 
单选题 ( 1.0 分) (组内4/5) 切至整卷模式 搜藏此题  
  A turntable is supported on a Teflon ring of inner raix;/ y oir; z5k*nao/jdius $R$ and outer radius $R+\sigma(\sigma << R)$, as shown in the diagram. To rotate the turntable at a constant rate, power must be supplied to overcome friction. The manufacturer of the turntable wishes to reduce the power required without changing the rotation rate, the weight of the turntable, or the coefficient of friction of the Teflon surface. Engineers propose two solutions: increasing the width of the bearing (increasing $\sigma$ ), or increasing the radius (increasing $R$ ). What are the effects of these proposed changes?



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25#
 
单选题 ( 1.0 分) (组内5/5) 切至整卷模式 搜藏此题  
  A hollow cylinder with a very thin wall (like a toilet paper tube) and a blo.csx *r fa9l -6pw* (utv5wsvtck are placed at rest at the top of a plane wis65tx (v*capvwu*sr. f t-wl9th inclination $\theta$ above the horizontal. The cylinder rolls down the plane without slipping and the block slides down the plane; it is found that both objects reach the bottom of the plane simultaneously. What is the coefficient of kinetic friction between the block and the plane?

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